The present invention relates to processes and compositions using rice hull in the manufacture of thermoplastic compositions for the production of articles having increased heat, water, fungal, and insect resistance. This product, the new thermoplastic composition is called "Hodapen pulp". However, for the convenience of disclosing the material in this invention, the terms Hodapen and thermoplastics composition are used interchangeably.
Rice is one of the most abundant grains and plays an important dietary role throughout the world. According to the Food and Agricultural organization of the United States, annual rice production was estimated to be in excess of 40,000,000 metric tons. A major derivative of rice production is the rice hull. The rice hull is a fibrous, non-digestible commodity, representing about 20 percent by weight of the harvested rice paddy. Typically, the dried rice paddy yields by weight, 52% white rice, 20% hull, 15% stalk, 10% bran. Generally, about 3% is lost in conversion. Rice hull resulting from such production generates a substantial disposal problem.
Rice hull has a striated configuration. The outer surface is composed of dentate rectangular elements having high silica content covered with thick cubicle and surface hair. The inner surface is composed of elongated hypodermal fibers substantially devoid of silica. The mid-region is transitional contains little silica. Overall, the rice hull is composed of silica, carbohydrates, proteins, fats and other minor organic constituents.
Rice hull is highly abrasive, poor in nutritive value, and low in bulk density. Accordingly, a few viable economic applications for this byproduct have been developed notwithstanding a widespread environmental desire to eliminate the customary disposal through burning and landfill. Burning, in particular, presents significant problems. Rice hull does not readily combust unless burned in highly controlled equipment that allows continuous removal of ash. Such equipment is costly and not widely available to the growers throughout the world. Particularly, when burning is conducted unattended in the fields, the long lasting, inefficient combustion presents fire hazards. The burning process also generates considerable smoke and airborne pollutants. The low bulk density of rice hull makes transportation to off-site burning facilities expensive, and the low fuel value of the rice hull is not commercially attractive. The low in bulk density also makes landfill disposal expensive.
To overcome these environmental and disposal problems, substantial effort has been undertaken to find new markets for the rice hull product. However, because of the aforementioned abrasiveness of the hull, lack of nutritive value, low bulk density, utilization has been limited to low value applications, such as bedding, litter, animal roughage and absorbents. While bedding and litter once were beneficial uses for the rice hull, particularly in poultry operations, other manufacturing byproducts such as wood shavings have reduced its demand. Litter usage is also adversely affected by remaining rice residue in the hull and its particulate aspiration and attractiveness to organisms, parasites, fungi, and the like. Numerous efforts have been made to use rice hull as feed for economic animals. Limited success has been achieved in this area due to the low digestibility and low nutritive value of the bull.
Efforts have also been made to utilize rice hull in other areas of the industry. For instance, the hull has been used as oil absorbent and its ash has been used in the cement industry, but there has been limited success due to its cost effectiveness applications.
As a result, a need has continued to exist for value added environmentally acceptable uses of rice hull in foregoing the customary burning and landfill disposal alternatives.
Finally, the present invention not only has overcome the inherent difficulties of utilizing rice hull for applications beyond the low value approaches, it has also incorporated plastic wastes and scraps, an environmental problem, into a composition to produce articles with excellent strength, properties, and final finish.
Due to lignocellulosic content of rice bull, it has lead to it being capable of being lumped with other like materials including grains, fibers, wood flakes and other similar cellulosic byproducts for possible combinations with other recycled materials for variety of applications. For instance, Nagich U.S. Pat. No. 5,480,602 suggests that rice hull together with plastics be used for extrusion of particleboard. Bistak et al. U.S. Pat. No. 4,747,688 suggests the use of rice hull as a cellulosic particulate component with plastic scrap to make thermoplastic molding compositions.
Montegi et al. U.S. Pat. No. 4,783,493 suggest the use of rice hull blended with thermoplastic resins for molding compositions. Moteki et al. U.S. Pat. No. 4,761,451 suggest rice hull as filler for the manufacture of acoustics vibration sheet. Parade et al. U.S. Pat. No. 5,002,713 and Maki et al. U.S. Pat. No. 4,882,112 suggests the use of rice hull in a moldable thermoplastic resin for use as flake board of particleboard panels and other shaped articles.
In the foregoing proposals, prime focus has been on cellulosic materials other than rice hull, notwithstanding peripheral mention of the possible use, few specific disclosures have been made for rice hulls usage in view of its many adverse properties that detract from its ability to simply replace other lignocellulosic materials. On the other hand, this invention exclusively deals with rice hull and not any other lignocellulosic materials. Moreover, although particleboard could be numerated as one of Hodapen's final products, the object of the invention is not to produce particleboard. In this invention the rice hull must undergo a chemical treatment process to adapt to the composition.